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A chlorine atom contains 17 electrons, 18 neutrons and 17 protons - Edexcel - GCSE Chemistry Combined Science - Question 5 - 2018 - Paper 1
Question 5
A chlorine atom contains 17 electrons, 18 neutrons and 17 protons. (i) State the mass number of this chlorine atom. (ii) Give the electronic configuration of this ... show full transcript
Worked Solution & Example Answer:A chlorine atom contains 17 electrons, 18 neutrons and 17 protons - Edexcel - GCSE Chemistry Combined Science - Question 5 - 2018 - Paper 1
Step 1
(i) State the mass number of this chlorine atom.
Answer
The mass number of an atom is the sum of the number of protons and neutrons. In this case, the chlorine atom has:
- Protons: 17
- Neutrons: 18
Thus, the mass number can be calculated as:
Therefore, the mass number of this chlorine atom is 35.
Step 2
(ii) Give the electronic configuration of this chlorine atom.
Answer
The electronic configuration of a chlorine atom (which has 17 electrons) arranges the electrons into energy levels. The configuration can be expressed as:
This notation indicates that there are 2 electrons in the first shell, 8 in the second shell, and 7 in the third shell. Hence, the electronic configuration of this chlorine atom is 2.8.7.
Step 3
(b) Describe what you would see if damp, blue litmus paper is placed into chlorine gas.
Answer
When damp, blue litmus paper is exposed to chlorine gas, it will undergo a color change. Initially, the blue litmus paper is blue, but it will turn red upon exposure to chlorine due to its acidic properties. The following observations can be made:
- The blue litmus paper will turn red.
- After some time, the paper may bleach to become white, indicating a strong bleaching action of chlorine gas.
In summary, the sequence of color change would be:
- Blue litmus paper turns red.
- Then, it bleaches and turns white.